1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, a developing apparatus used in the electrophotographic image forming apparatus, and a process cartridge detachably mounted to the electrophotographic image forming apparatus.
Here, the electrophotographic image forming apparatus refers to an apparatus for forming an image on a recording medium by an electrophotographic image forming method. Further, examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (such as a laser beam printer and a light emitting diode (LED) printer), a facsimile apparatus, and a word processor.
Further, a developing apparatus refers to an apparatus for visualizing an electrostatic latent image formed on an image bearing member such as an electrophotographic photosensitive member with the use of a developer.
Further, a process cartridge refers to a cartridge into which charging means, developing means or cleaning means, and an image bearing are integrally incorporated, the cartridge being detachably mountable to a main body of an electrophotographic image forming apparatus. Moreover, a process cartridge refers to a cartridge into which at least charging means and an image bearing member are integrally incorporated, the cartridge being detachably mountable to a main body of an electrophotographic image forming apparatus.
2. Description of the Related Art
Conventionally, in an electrophotographic image forming apparatus employing an electrophotographic image formation process, an electrophotographic photosensitive member and process means which acts on the electrophotographic photosensitive member are integrally incorporated into a cartridge.
Then, a process cartridge system in which the cartridge is detachably mountable to a main body of an electrophotographic image forming apparatus is employed. The process cartridge system enables a user to do maintenance of an electrophotographic image forming apparatus without relying on a service person. Thus, the marked improvement in operability of the electrophotographic image forming apparatus can be obtained.
One of the primary conditions for process cartridge replacement is developer depletion (out of developer). In such a case, in order to prompt a user to timely replace process cartridges by giving the user the information regarding a developer remaining amount in advance, the developer remaining amount in a process cartridge has been detected by various methods in recent years.
One of the various methods is a light transmissive type developer remaining amount detection. In the light transmissive type developer remaining amount detection, a detecting light passing inside the process cartridge is detected based on a length of time during which a toner within a container blocks the detecting light. There are some process cartridges having a light emitting guide portion and a light receiving guide portion provided therein as means for guiding the detecting light into the process cartridge. The light emitting guide portion guides a detecting light emitted from a light emitting portion such as LED, which is attached to the electrophotographic image forming apparatus main body or the like, into the process cartridge. The light receiving guide portion guides the detecting light, which has been introduced into the process cartridge, to a light receiving portion such as a phototransistor attached to the electrophotographic image forming apparatus main body or the like. The light emitting guide portion and the light receiving guide portion are separately attached to the process cartridge (Japanese Patent Application Laid-Open No. 2003-131479).
If the light emitting guide portion and the light receiving guide portion are separately provided, the number of components and the number of the manufacturing steps for assembly are increased. Accordingly, there is proposed a process cartridge in which the light emitting guide portion and the light receiving guide portion are integrated (Japanese Patent Application Laid-Open No. 2003-167490).
For example, when a light transmissive member integrating the light emitting guide portion with the light receiving guide portion for detecting the developer remaining amount as described above is made of only a transparent material, the accuracy of the developer remaining amount detection may be reduced.
Specifically, there is a case where light which is emitted from a light emitting element provided in the apparatus main body enters from portions other than the light emitting guide portion, and hence an amount of the light is increased, or where a reflected light reflected from outer walls other than incident surfaces and exit surfaces of the guide portions is detected by a light receiving element provided in the apparatus main body.
In order to avoid the above-mentioned case, there are proposed countermeasures such as providing a hood on the light receiving element for the purpose of preventing an unnecessary reflected light from entering the light receiving element, replacing the light emitting element with a light source emitting a parallel light instead of a diffusion light, and covering portions other than the light emitting guide portion and the light receiving guide portion of the light transmissive member with a frame or the like forming a container. However, it is conceivable that component cost is increased in the case of using a parallel light, and that the size of the electrophotographic image forming apparatus becomes larger in the case of covering the portions with a hood or a container frame.